Rolf Olsson is an unlikely contender to bring about a technological revolution in the dating industry. After all, this avuncular-looking chappie is a 71-year-old grandfather. But you have to give it to Rolf. This septuagenarian has - excuse the pun - his finger well-placed on the button of modern dating. He is also possibly about to make a killing of the most lucrative kind in what is a burgeoning industry.

Rolf is an inventor and his baby is the Smart Heart. This is an electronic dating device modelled on the Japanese Tamagotchi, which will go on sale this month in the UK for about pounds 50 - the price of a Game Boy. It's a modest amount to part with when you compare it to the cost to the price of a Dateline subscription, which is currently pounds 150 and offers you six initial dates. For your 50 quid, you are guaranteed as many dating hits as serendipity will send you.

The Smart Heart works like a singles' radar, storing data and sending out signals to other gizmos in the area. You input the criteria of your perfect partner such as age, interests, profession, education, and assign each quality a level of importance. You also specify what type of relationship you're looking for, eg long-term, short fling or one-night stand. Then you walk the streets hoping that someone single, in possession of a Smart Heart and an equal sense of Nineties irony, matches your criteria. The gizmo vibrates and a phone number flashes on your LED. Bob's your date.

Of course, the success of the Smart Heart as a dating service is based entirely on whether enough people will buy it - essentially, on whether it becomes a cult. But there are a lot of single people knocking around who, more than ever, are choosing to be consumers of dating services. At the last official count in 1995, there were over six million single men and women in their dating prime (25-44 years of age) in England and Wales. That's the market that companies like Rolf's are targeting.

Technology is about to blow a whole lot of dust off the UK dating industry. How stagnant this industry has been becomes apparent when you look back to 1966, when Dateline, the country's first national introductions agency, was launched. In the subsequent 30 years, progression has been sludgy at best. Up until recently, the only alternative to joining a regional or national dating agency was to place an ad in a lonely hearts column - personals in a newspaper inviting respondents to write to a box number. The phrase "lonely hearts", itself only shrugged off in the last five years, was a marketing anachronism and carried the full, dead weight of stigma with it.

But enough history. Fast-forward to 1998, and lonely hearts are still around, but they now come in the guise of voicemail personals. The inverse of estate agents, voicemail personals work by tapping the market at no cost to the advertiser. The single person - the advertiser - places an ad in a paper for free, and interested punters call up a premium rate line, hear more information and leave a message. Charge bands range from 25p to pounds 1.50 per minute. More and longer messages mean more revenue for the service provider, a proportion of which goes into a publisher's classified ads revenue.

Not surprisingly, this is a transatlantic import and the three companies that provide telephone-based dating services for all our national and regional papers are all American. Every national paper except the Daily Mail now carries voicemail personals. Like the faithful tortoise, the Daily Mail is also thinking about jumping aboard.

More portentously, November will see Cosmopolitan and Esquire - two leading National Magazines glossies that target ABC1 readers in their twenties - launch voicemail personals too. Close Encounters will introduce Cosmo girls to Esquire boys - quite possibly the start of a beautiful, tailor- made relationship. "I think it will be a phenomenal success," says Cindy Asplande, commercial manager for Advanced Telecom Services, who are voicemail dating service providers for National Magazines as well as Time Out, the Evening Standard and the Guardian. "It's a big step for them, but in terms of hitting a new market I think Cosmo and Esquire will open the floodgates."

The floodgates are indeed opening fast as publishers hook onto the fact that single people with disposable incomes are a gaping market waiting to be tapped. Although there are no figures for the telephone dating industry alone, OFTEL did conduct research into the revenue from premium rate calls in the UK in 1996/97 and found that 400 million minutes were logged. "I would have thought that telephone dating accounts for at least half of that amount," says Andrew Lindenmayre, marketing executive at ATS. "That's a 'guestimate', but it's an educated one."

Given that the average duration of a call to a voicemail box is one minute, and most calls come in at around 50p, we have a ballpark figure of at least pounds 100 million in annual turnover for voicemail personals for 1996/97. That's before the glossies - with the greatest potential market of consumers - have come in on the act.

From the ashes rises the phoenix, but how can it be that personals have suddenly turned around? The answer lies as much in marketing as in technology. "Previously, Cosmo and Esquire wouldn't have touched personal ads, they were beneath them," says Cindy Asplande. "But these days personals look much more professional in print, and branding is a real strength." The answer also lies in the recent change in British cultural attitudes towards being single. Post-Bridget Jones, we all look a little more indulgently - affectionately, even - at the plight of the poor professional singleton.

While UK publishers have just started cranking themselves up in the voicemail market, the dating revolution on the Internet is already over two years old. And the growth rate of online dating leaves print and phone-based services spitting in the ether.

Cosmo's pre-launch run attracted 87 advertisers - in Cindy Asplande's view, an extremely promising, if not glowing, start. Of course, you need to multiply this figure by the number of calls one ad will receive. If 100 calls are logged for just one ad, that's 8,700 punters coughing up on that premium rate line. The only question you'll probably be asking is why British companies haven't caught on to it sooner.

Now digest this little vision of the future-past. Swoon is a global dating website run by Conde Nast US (publishers of GQ and Vogue) that offers a free personals service. It currently holds 100,000 people on its database - that is, advertisers who have posted an online personal - and that figure is constantly growing. This also doesn't include the 250,000 page views per day - individual accesses to advertisers' ads.

Look at the site (www.swoon.com) and it's easy to understand why Swoon works. Advertisers fill in an online form which is tailormade for the Friends and This Life and Ally McBeal modern single. While our pedigree chum Dateline asks clients coyly whether they like "pop, rock, jazz or folk", Swoon tells you to list what's in your CD player. Dateline asks you whether you drink and smoke "often, occasionally or never". Swoon tells you to rate your booze, fags and (shock!) drugs quota in a "sin index". You can respond via e-mail - re-routed through Swoon servers to preserve your anonymity - to as many ads as you like, or wait for responses to drop into your mailbox.

With its ironic retro design, and editorial tone which skips hand in hand with the zeitgeist, Swoon does the hitherto impossible - it makes lonely hearts cool. "Swoon is kind of like the Village Voice used to be," says editor-in-chief Melissa Weiner. "In its heyday the Voice ran personals and everyone used them because they were cool. We're a cool site editorially and artistically. And it really is for the users. Unlike other dating sites, you can search the database without having to register. We don't force people to place ads. And we're free."

How long Swoon will remain a free service is debatable. When launched in July 1998, there were no tried and tested, subscription-based online dating services in place - primarily because credit card transactions were not yet secure on the web. CondeNet's agenda was to create a thriving online community first, with a pay-per-use service possibly being phased in later.

Two years down the line, secure technology has opened the doors to internet dating as a fully-fledged consumer service, and nearly 300 dating websites are now jostling for the worldwide online singles market. Swoon is the Loaded of the online dating industry, and like any good product with a great formula, it's only a matter of time before the serious competition muscles in. So far, emulators have been confined to the United States, where the bulk of dating services users reside - and have a pretty good chance of meeting other users in their catchment area. While web dating in theory has no geographical boundaries, long-distance virtual relationships rarely succeed. Nick, 29, an advertisting sales executive from London, dated Susie, a 24 year-old post grad student in Alabama, for six months. "After endless e-mails and phone calls and three transatlantic trips I decided I really, really liked her, but didn't actually fancy her. End of story. It did leave a hole in my pocket, and it's not something I'd do again."

But Nick would try it again if there was a homegrown online dating service - and as e-commerce would have it, he's about to get a second shot. British GQ, one branch of the Conde Nast empire, are planning to launch a third- party dating website based on Swoon in the new year - effectively leapfrogging ahead of Cosmo and Esquire in the technology stakes. "It's sort of under wraps," said Olivier de Peretti-Clarke of GQ Online. "All I can say now is that it's going to be a personals service with a commercial tie-in, and people will be able to post a personal ad." If it works as well as Swoon, GQ's online dating service will grab all those singles in their twenties and thirties who are hooked up to the net at work and have an hour's dead lunchtime to kill. They will not necessarily be GQ readers - in fact, they could as easily be Esquire readers. What they will all like is the rapid response time, the buzz you get from feeling like you're in a sweet shop and can take away a fistful of candybars in one go.

ATS, our voicemail friends, are also launching a UK dating website - by the end of this year, in fact. National newspaper websites will have hotlinks to ATS's central database (with its own, independent front door) where subscribers will be able to meet other singles who read the same paper, or even other papers. The prospect of Guardian readers cross-fertilising with Telegraph readers is an interesting one, though you can't help thinking that the Yanks have somehow grasped, yet profoundly missed, the point.

The one great thing that ATS's website will address is the problem of locality. By using a postcode-based search engine, users will be able to locate potential dates in any given radius from their home - the time- honoured, short-shot principle that Rolf OIlsson's Smart Heart, and ye olde Dateline, is based on.

You might now wonder where this leaves Dateline. "We have our own website now," says Peter Bennett, marketing manager, "and that's the fastest-growing element of the service, it's doing really well." Unfortunately, it doesn't work. Surfers can input partner preferences and run a database search (which yields double-entendre gems such as "This 28-yr-old, well-built, highly attractive member..."), but to join they must go the weary paper route. Which means ticking off checkboxes on a form with crude and dated categories. For example, "at home" interests are: listening to music, reading, watching TV, watching TV sport, listening to the radio, being with children, cooking/entertaining. DIY/crafts, gardening, animals. Not quite Bridget's - or anyone under 50's - thing. "It's mainly for reasons of security that we haven't launched a full online service yet," says Peter. "But we're not ruling it out." Dateline have yet, it seems, to wake up and smell the Nescafe. Unlike Rolf, who, you have to admit, at 71 is pretty quick off the mark. But then he is German. Vorsprung durck technik.